WASHINGTON (Reuters) – Federal prosecutors in New York are examining whether U.S. President Donald Trump’s former lawyer, Michael Cohen, committed tax fraud in relation to his taxi-medallion business, the Wall Street Journal reported on Tuesday.

Cohen, who was Trump’s personal lawyer, has not been charged with any crime. The FBI seized documents and files as part of investigations by federal prosecutors in New York stemming in part from a referral by the U.S. special counsel’s office looking into possible coordination between Trump 2016 campaign aides and Russia.

Moscow denies interfering in the U.S. election and Trump denies collusion by his campaign, describing the probe as a political witch hunt.

Asked for comment, Lanny Davis, an attorney for Cohen, said “in light of ongoing investigation, I am unable to respond.”

Federal authorities are assessing whether income from Cohen’s taxi-medallion business was underreported in federal tax returns, according to the newspaper, citing one person familiar with the matter.

In New York, licensed cabs must display a medallion, a metal badge sold by the city. Before the advent of ride-hailing services like Uber, the medallions were a potentially lucrative investment.

Authorities are also looking into whether any bank employees improperly allowed him to obtain loans without adequate documentation, including whether Cohen inflated the value of assets used as collateral for loans, as well as whether he lied on his loan applications, the Journal reported, citing multiple people familiar with the matter.

Fraud charges could increase pressure on Cohen to cooperate with prosecutors in the Russia case.

Reuters has previously reported Cohen is being investigated for possible bank and tax fraud, and possible campaign law violations linked to a hush money payment to porn star Stormy Daniels, citing a person familiar with the probe.